1. Field of Invention
The present invention relates to copper-based sliding material and method for producing the same. More particularly, the present invention relates to an improvement in the sintered sliding material consisting essentially of copper, graphite and alumina.
2. Description of Related Arts
Such alloys as bronze, lead bronze and kelmet have heretofore been used as the copper-based sliding material. Every one of these materials exhibits the sliding characteristics only under the condition where abundant lubricating oil is present. The sliding characteristics of these alloys are unsatisfactory under a severe lubricating condition, i.e., the boundary lubricating condition, so that such damages as the wear and seizure occur in a short period of time on the sliding surface. Accordingly, the resin bearings, representative of which is the polytetrafluoroethylene, and bearings made of metal and graphite, the latter being embedded on the sliding surface of the former, are used, since the sliding characteristics of these materials are exhibited under the boundary lubricating condition. However, the sliding characteristics of these materials are poor from the view points of wear-resistance and seizure resistance. Accordingly, the present inventors paid attention to Japanese Unexamined Patent Publications Nos. 61-67,736, and 60-106,932, which propose the sliding material consisting essentially of copper, graphite and alumina, and which disclose the reduction in coefficient of friction due to graphite and the increase in wear-resistance due to alumina. The present inventors thus studied the sliding characteristics of these materials.
It turned out as a result of the investigation present inventors that, when the copper-graphite-alumina series material produced by an ordinary sintering method is subjected to the wear-resistance test and seizure-resistance test under the boundary lubricating condition, alumina is separated from the sliding surface to deteriorate the sliding characteristics.